Re: [PATCH stable 4.9] net: stmmac: Set dma ring length before enabling the DMA

[Sasha Levin <sashal@kernel.org>]

On Fri, Apr 12, 2019 at 04:21:31PM +0200, Lars Persson wrote:
>
>
>On 4/12/19 4:16 PM, Sasha Levin wrote:
>>On Fri, Apr 12, 2019 at 01:17:05PM +0200, Lars Persson wrote:
>>>This was fixed in upstream by commit 7d9e6c5afab6 ("net: stmmac: Integrate
>>>XGMAC into main driver flow") that is a new feature commit.
>>>
>>>We found a race condition in the DMA init sequence that hits if the
>>>PHY already has link up during stmmac_hw_setup. Since the ring length
>>>was programmed after enabling the RX path, we might receive a packet
>>>before the correct ring length is programmed. When that happened we
>>>could not get reliable interrupts for DMA RX and the MTL complained
>>>about RX FIFO overrun.
>>>
>>>The correct init sequence according to the data book for DWC Ethernet
>>>QoS 4.10 is:
>>>1. Write Ring length
>>>2. Write Descriptor list base address
>>>3. Start the DMA.
>>>
>>>Signed-off-by: Lars Persson <larper@axis.com>
>>>Cc: stable@vger.kernel.org # 4.9.x
>>>Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
>>>Cc: Alexandre Torgue <alexandre.torgue@st.com>
>>>Cc: Jose Abreu <joabreu@synopsys.com>
>>
>>What about 4.14? 7d9e6c5afab6 isn't in it either.
>>
>
>I will send a separate patch for 4.14 in some days.

Okay. I can't merge this one until we have the 4.14 as well (otherwise,
people who upgrade from 4.9 to 4.14 will see a regression), so when it's
posted I can do both.

--
Thanks,
Sasha